Vehicle powertrains and other complex torque-generating systems are typically controlled in response to a requested output torque as a function of the system's available output torque. Torque-based control, also known as control in the torque domain, provides a single control degree of freedom in the form of available output torque. For example, conventional vehicle powertrains are controlled in the torque domain using a driver's output torque request, which in turn is determined as a function of torque request level and calibrated set of powertrain-unique gear mapping.
By way of contrast, in a power domain-based control system, or control of a system in the power domain, a controller considers the total amount of mechanical power that can be generated by any number of torque-generating devices of the system, such as internal combustion engines and electric motors, as well as all power losses incurred in the system. Control in the power domain provides two control degrees of freedom, i.e., both torque and speed. As a result, power domain-based control may be particularly useful when applied to hybrid electric powertrains and other complex systems having more than one torque-generating device.